The present invention relates to a control system for activating a piezo-electric speaker through the use of output signals derived from a microcomputer.
The present invention relates, more particularly, to a speaker drive control system in a microwave oven which includes a microcomputer as a control circuit.
A microcomputer implemented with a P-channel MOS LSI is widely used in electronic apparatus such as a digital control circuit of a microwave oven because the P-channel MOS microcomputer can directly drive a fluorescent display panel of the dynamic drive type. However, the P-channel MOS microcomputer has a considerably low calculation speed. Therefore, it is difficult to develop a frequency signal for driving a piezo-electric speaker from the P-channel MOS microcomputer while the P-channel MOS microcomputer develops the drive signal to the fluorescent display panel and conducts the time keeping operation for timer operation purposes or for current time keeping purposes.
The piezo-electric speaker is employed in the microwave oven for audibly indicating the cooking completion or for audibly developing a confirmation sound when the key input operation is conducted through a key input panel in order to introduce a cooking source selection signal, cooking temperature set information or cooking time period information.
Accordingly, an object of the present invention is to provide a piezo-electric speaker drive control system which utilizes a control signal developed from a P-channel MOS microcomputer.
Another object of the present invention is to provide a piezo-electric speaker drive system in a microwave oven which includes a digital control system implemented with a P-channel MOS microcomputer.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, two output signals are applied from a microcomputer to a piezo-electric speaker drive system. One signal is a frequency signal for activating a piezo-electric speaker. The other signal is a timing control signal for selectivity applying the frequency signal to the piezo-electric speaker. Since the frequency signal is always developed from the microcomputer, the time period before the piezoelectric speaker is actually activated is considerably reduced.